title: Preliminary study of kaonic deuterium X-rays by the SIDDHARTA experiment at DAΦNE.
abstract: The study of the [Formula: see text] system at very low energies plays a key role for the understanding of the strong interaction between hadrons in the strangeness sector. At the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati we studied kaonic atoms with [Formula: see text] and [Formula: see text], taking advantage of the low-energy charged kaons fromΦ-mesons decaying nearly at rest. The SIDDHARTA experiment used X-ray spectroscopy of the kaonic atoms to determine the transition yields and the strong interaction induced shift and width of the lowest experimentally accessible level (1s for H and D and 2p for He). Shift and width are connected to the real and imaginary part of the scattering length. To disentangle the isospin dependent scattering lengths of the antikaon-nucleon interaction, measurements of [Formula: see text] and of [Formula: see text] are needed. We report here on an exploratory deuterium measurement, from which a limit for the yield of the K-series transitions was derived: [Formula: see text] and [Formula: see text] (CL 90%). Also, the upcoming SIDDHARTA-2 kaonic deuterium experiment is introduced.
authors.affiliation: INFN, Laboratori Nazionali di Frascati, C.P. 13, Via E. Fermi 40, I-00044 Frascati (Roma), Italy.
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authors.lastname: Beer
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authors.lastname: Berucci
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authors.lastname: Bragadireanu
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authors.lastname: Guaraldo
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authors.lastname: Iliescu
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authors.lastname: Ishiwatari
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authors.lastname: Iwasaki
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authors.lastname: Kienle
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authors.initials: P
authors.lastname: Levi Sandri
authors.forename: A
authors.initials: A
authors.lastname: Longoni
authors.forename: J
authors.initials: J
authors.lastname: Marton
authors.forename: S
authors.initials: S
authors.lastname: Okada
authors.forename: D
authors.initials: D
authors.lastname: Pietreanu
authors.forename: T
authors.initials: T
authors.lastname: Ponta
authors.forename: A
authors.initials: A
authors.lastname: Romero Vidal
authors.forename: E
authors.initials: E
authors.lastname: Sbardella
authors.forename: A
authors.initials: A
authors.lastname: Scordo
authors.forename: H
authors.initials: H
authors.lastname: Shi
authors.forename: D L
authors.initials: DL
authors.lastname: Sirghi
authors.forename: F
authors.initials: F
authors.lastname: Sirghi
authors.forename: H
authors.initials: H
authors.lastname: Tatsuno
authors.forename: A
authors.initials: A
authors.lastname: Tudorache
authors.forename: V
authors.initials: V
authors.lastname: Tudorache
authors.forename: O
authors.initials: O
authors.lastname: Vazquez Doce
authors.forename: E
authors.initials: E
authors.lastname: Widmann
authors.forename: J
authors.initials: J
authors.lastname: Zmeskal
keywords: Atomic physics, [Formula: see text], [Formula: see text]; deduced kaonic atoms X-ray K-series yields to be used for low-energy QCD; measured X-ray spectrum using SDDS at SIDDHARTA-2